Intestinal spirochaetosis (IS), also known as colonic spirochaetosis or spirochaetal diarrhoea, is an important production-limiting disease of pigs and adult layer and broiler breeder hens. IS results from infection of the large intestine with the intestinal spirochaete Brachyspira (formerly Serpulina) pilosicoli. This spirochaete also infects a number of other animal species, including dogs, as well as human beings. The associated disease is best understood and has been most studied in pigs.
The prevalence of the infection in the Australian pig industry is uncertain, but studies in Europe and Scandinavia suggest that 30% or more of pig herds are infected. The associated disease is a colitis/typhlitis with intermittent diarrhoea and reduced growth rates. The economic significance of the disease in pigs is not clear, but it may be large since, although it is milder than swine dysentery, it is generally much more prevalent.
B. pilosicoli also commonly infects adult chickens. In a recent survey in Australia, intestinal spirochaetes were recovered from 43% of broiler breeder flocks and 68% of layer flocks, and B. pilosicoli was the spirochaete involved in 44% of a subset of these flocks. Infected flocks had an average 14% wetter faeces than uninfected flocks. Experimental infection of broiler breeder hens with a B. pilosicoli isolate from this study resulted in a significant delay in onset of egg production and a sustained reduction in egg production. Besides layers, loss of egg production in broiler breeder flocks can cause considerable disruption to the whole broiler industry. The costs of these problems are difficult to estimate, but the Industries are significant in Australia. The Chicken Meat Industry produces meat with a retail value of $2.5 billion, whilst the Egg Industry produces eggs valued at $340 million.
The role of B. pilosicoli as a pathogen of dogs and other animal species is still not firmly established, although it seems likely that it is capable of impacting on health to a greater or lesser extent depending on a number of other factors. B. pilosicoli also infects large numbers of people in developing countries. In developed countries infection is mainly confined to immunocompromised individuals and homosexual males. It has been recorded as a cause of spirochaetaemia in elderly and/or immunocompromised individuals. The full extent of the pathogenic impact of B. pilosicoli in these human population groups is still debated.
Few attempts have been made to develop means to control infections with B. pilosicoli. When IS is identified as a problem in piggeries, animals are routinely treated with antimicrobials, although the disease tends to recur following withdrawal of treatment. However, the disease in chickens is not well understood, and the chicken industries have not specifically tried to control the infection.
There is only one recorded study of the use of a vaccine to control IS in pigs and this autogenous bacterin failed to offer protection (Hampson D J, Robertson I D, La T, Oxberry S L and Pethick D W (2000) Influences of diet and vaccination on colonization of pigs by the intestinal spirochaete Brachyspira (Serpulina) pilosicoli. Veterinary Microbiology 74:75-84). Nevertheless, because there is a specific end-on attachment of the spirochaete to the large intestinal mucosa, it seems likely that colonisation can be reduced or prevented by the use of a suitable vaccine-induced immunity.
The present invention provides a novel B. pilosicoli amino acid sequence and the polynucleotide sequence that encodes it, which has not previously been identified.